That is pretty much the exact way that the old AVS sites worked, I think.
We would build what was essentially a free site and it would go behind the AVS doorway.
I am not sure what verification they had back then but the user did have to break out the credit card in order to access dozens of sites.
Not sure why it is not being implemented any more.
from 2003:
https://web.archive.org/web/20030415...art/slang.html
Voltar's Newbie Quick Start Guide
(Not just for Newbies)
The New Webmaster's Guide to Internet Slang
AVS
Adult Verification Service: Sets up a password-protected entrance. This is used to keep minors (and those without credit cards) out of your adult site. Often used as a source of traffic as well as making money from selling memberships into the AVS service.
Again from back in 2003, one of VNWR's newbie projects of the week:
https://web.archive.org/web/20030411...rafficavs.html
Newbie Project of the Week
Traffic and AVS sales
This week we will be building a couple small projects
for traffic generation and to add to your generation arsonal.
Everything should be made for serach engine (SE) submits
1. TGP templates
Start by visualizing the traffic flow of the surfers as they come to your page
Top to bottom
The first thing you want to do is have them see your first sponsor ad
So make a colored table with contrasting text color
Next is where you place recips. on a recip gallery
Now you have to decide how many pics/thumbs your going to use
12-20 would be a nice standard
Place approx. half of the thumbs next
They can be in a table or centered or even a pattern
Then another text ad for a sponsor
Important note: do NOT make it implie they are going to other galleries
Or even to get other pics. This is blind linking and will cost you listings
Make the text short and not to long, but tell them they are going to a sponsor
And make sure they know its Hot and the best thing since sliced bread
There are NO banners on this template. You will adjust the text to the sponsor you are advertising
Do NOT use other text on this template. If it doesn't make you money don't have it
Ok, next you place the rest of the thumbs.
Now a small link into your other site (your filter page or hub is fine)
2nd Template
12-20 pics/thumbs
One text ad and one banner ad with text on this gallery
Make one as the topper for the pics and one for the bottom for the pics
Get creative but not blind!
NO large or large odd sized banners under 20k, best under 15k for the banner
Make sure you tell the surfer that these are sample pics from the sponsor your using
This one is left so you get creative and unique.
Link straight to the pics only and not html pages on both these templates
2. AVS basic site
This will be a basic AVS NON-exclusive reg. site
Pick a catagory/niche
Pick your favorite AVS service and create a Front page to sale that AVS service
And your niche that your building for
Sell it hard. Think of this as your personal splash sales page, as it will be
NO ads on the front page except for the AVS service, You may offer a premium service of thiers
As well as the reg. one you really are selling, IF your allowed to and in this position
With the AVS service you choose. Do NOT ask me or the board.
This is a personal issue you will have to take up with your choice of AVS service.
If you do NOT understand about the premium upsale issue
Just skip it, as you will as you get more into AVS site building
It's one of those time and have to be there things so don't get stressed about it
Make sure you have some unlinked sample pics(low bandwidth)
Use a graphic program and make them fancy looking
Do NOT just throw them in raw bordered template and expect them to work
The AVS site
Front page, and two gallery pages with 15+ pics each and two sponsor links each
Sound a little like the galleries above don't they 
Just edit them so copies can serve as the inside gallerys
no main page, gallery one links to gallery two (this is a basic site)
The real tie in
One of the sponsor links on each of your TGP galleries will be for this AVS site
Advertise the site and its theme on the TGP page, NOT the AVS service
That comes on your splash/front page
It's ok to use the same pics on both
As when they get into the AVS service they will most likely get lost
In the large amount of sites they offer
Target everything to the niche your selling
You can make mirror Front pages for recips. to sites that allow AVS sites
Mirror the TGP galleries at least 3 times, OTHER than the no recip. one
And use 3-4 recips. on each of them.
Submit both TGP galleries and the front splash page to at least 10 SE's
Repeat for other niches
Enjoy traffic from TGP's, Link lists, SE's, and internal AVS link lists
What more for traffic generation could you ask out of a project